Colorectal cancer, also called bowel cancer, colon cancer, or rectal cancer, is a type of cancer that begins in the colon or rectum, parts of the large intestine. It arises from the uncontrolled growth of cells in the colon or rectum that can invade or spread to other parts of the body. It often starts as benign growths called polyps on the inner lining of the colon or rectum, which can over time become cancerous. The cancerous process usually involves genetic mutations that disrupt normal cell regulation. Common signs and symptoms may include blood in the stool, changes in bowel habits, unexplained weight loss, abdominal pain, and fatigue. Risk factors include lifestyle factors such as diet, obesity, smoking, lack of physical activity, and some genetic conditions as well as inflammatory bowel diseases. Screening methods such as colonoscopy are important for early detection and prevention by identifying and removing polyps before they turn cancerous. Colorectal cancer is one of the most common cancers worldwide, most often affecting people over 50 years old. Its prognosis depends on the stage at diagnosis, with early detection significantly improving survival chances. Treatments include surgery, chemotherapy, radiation, targeted therapy, and immunotherapy depending on the stage and specifics of the cancer. In summary, colorectal cancer is a type of cancer starting in the large intestine, often from pre- cancerous polyps, influenced by genetic and environmental factors, and detected early through screening to improve outcomes.